Metallurgical tuyere



Aug. 6, 1968 R. 1 w. HOLMES METAL-LURG I CAL TUYERE Filed DSC. l, 1965 ATTORNEY United States Patent* O v f 3,395,910- f METALLURGICAL TUYERE Ronald L. W. Holmes, New Providence, NJ., assignor to Union Carbide, Corporation, a corporation 4of 4New York Filed Dec. 1, 1965, Ser. No. 510,772

5 Claims. (Cl. `26E-41) l nozzle into the bath, whereby the refractory material serves to prevent molten material from coming into contact with the metal parts of the tuyere.

This invention relates to a metallurgical tuyere and more particularly to a submerged tuyere for injecting a gas below the surface of a molten metal bath.

The main object of the invention is to provide a tuyere which will exhibit a relatively long life when exposed to a high temperature bath of molten metal such as steel, even though such tuyere is not water cooled.

Another object is to provide a tuyere which will not readily become plugged with molten metal during its operation.

Still another object is to provide a tuyere which in addition to satisfying the foregoing -objects will also enable the gas to be discharged at about its critical velocity.

Other objects and advantages of the invention will suggest themselves from the remaining disclosure, drawing and appended claims.

In the drawing:

FIGURE 1 is a sectional view of the tuyere of the inventi-0n when in operative position below the surface of a molten metal bath in a degassing vessel, and

FIGURE 2 is an isometric view of a portion of the injection tuyere shown in FIGURE l.

In brief, the apparatus of the invention consists of a central conduit for conduct-ing a ow of gas, e.g. argon, from a source of gas supply, such conduit having an inlet end and a discharge end. Connected to the discharge end of this conduit is a nozzle of smaller diameter than the central conduit. The nozzle is sized so that the gas will be discharged at critical velocity at the flow rate of gas expected to be injected into the molten metal.

A sheath of refractory surrounding the nozzle is utilized to protect the nozzle from actually coming into contact with the molten metal.

Preferably, a highly conductive metal stopper member is disposed within the central conduit adjacent its inlet end. In the event there is a sudden failure in the gas supply pressure and molten metal enters the nozzle and central conduit, this stopper member will prevent the molten metal from flowing into the gas supply lines. Another advantage of this stopper member is that its removal enables one to insert a cleaning tool axially through the central conduit and nozzle in order to clean same if it becomes partially plugged.

As a still further safety measure, it is preferable to employ a length of heavy pipe extending upwardly be- Patented Aug. 6,1968

tween vthe inlet end of the central conduit and the gas supply means. The length of this pipe' should be greater than the anticipated height of molten metal in the de- Vgassing vessel so that the gravity effect will be neutralized and molten metal will not be able toenter the gas supply system. l

Referring tov the drawing, the tuyere 10 of the invention is shownpositioned at the bottom ofa degassing vessel 11 having a lining 12. The tuyere consists of a centralA conduit 15 having an inlet end 16 and a discharge end 17. The inlet end -16 is connected to an upwardly ex- Y tending length of heavy pipe 18. The lengthA of pipe 18 is' preferably greater than the expected head of molten met'- al in the degassing vessel. The upper end of pipe '18 is connected via conduit 19 to a gaseous supply means such as "a tank-of pressurized gas. The discharge end"'17l of central conduit 15 has a tuyereV nozzle 20 connected thereto. The diameter of tuyere nozzle 20 is sized so as to provide'critical flow at the flow rates anticipated which will be required for a particular degassing process. The nozzle 20, along with the exposedportion o f central conduit 15, is encased with a sheath of low grade refractory cement 21 which in turn is su-rrounded by a sheath of high grade refractory brick 22. The refractory brick 22 is secured to the side of the vessel lining by a refractory fillet 23. When the refractory cement 21 is applied it is molded so as to provide a discharge passage 24 extending axially from the discharge end of nozzle 20. The diameter of this discharge passage is also preferably of the same diameter as the diameter of nozzle 20. The overall sheath of refractory serves to prevent molten metal from coming into contact with the exposed surfaces of the tuyere, thereby prolonging the life of the tuyere, though it is not water cooled. The refractory sheath, however, is usually replaced after every heat.

In operation, the refractory sheath as well as the pressure of the gas discharged from the tuyere prevent molten metal from entering or otherwise contacting the metal surfaces of the tuyere. When the ow of gas is stopped, the gas between the shut-off valve (not shown) and the tuyere nozzle 20 escapes into the molten metal until the pressure in the tuyere is equal to the ferrostatic pressure. Within a few seconds thereafter, some of the metal freezes at the face of the nozzle 20'. In most cases, however, the metal freezes in the molded port 24, just short of the tuyere nozzle, and thus only the refractory sheath would be replaced between heats.

In the event of a sudden loss of gas pressure, molten metal would enter the metal portions of the tuyere. As a safety precaution, a high conductive stopper rod member 26 is positioned adjacent the inlet end of central conduit 15 so as to cause the molten metal to freeze at this point and prevent it from entering the gas supply lines. The stopper rod member 26 may be formed of copper or other highly heat conductive material.

The stopper rod member 26 is also positioned axially of the central conduit 15 so that when the rod is removed it will enable one to insert a cleaning tool to remove a partially plugged up tuyere tube or nozzle.

As a still further safety precaution, a length of heavy pipe 18 is positioned vertically between the inlet end of conduit 15 and the tubing 19 leading to the gas supply, the length of such pipe being preferably slightly greater than the anticipated height of molten metal to be held within the degassing vessel.

To provide an indication of the relative dimensions of the tuyere in a typical situation according to the invention, a tuyere having a central conduit 15 of 1/2 inch inside diameter, with a tuyere nozzle 20 of 0,220 inch inside diameter was successfully operated at a flow rate of 4,000 s.c.f.h. of argon. The low grade refractory cement 21 consisted essentially of about 30% alumina and 70% 3 silica. The high grade refractory 22 consisted essentially of an 80% alumina ramming refractory, balance silica. The tuyere was positioned about three feet beneath the surface of a molten steel bath in a degassing vessel having a capacity of about 90 cubic feet.

What is claimed is:

1. A metallurgical tuyere for submerged injection of inert gas into a molten metal bath, which comprises: a central conduit having an inlet end and a discharge end, a metal nozzle connected to said discharge end of said central conduit, said nozzle having a diameter which is smaller than the diameter of said central conduit, and a protective sheath of refractory material surrounding said nozzle and the immersed portion of said central conduit, said sheath of refractory material additionally forming a discharge passage extending axially from the discharge end of said nozzle for passing gas from said nozzle into said bath, whereby said sheath of refractory material prevents molten metal from coming into contact with said nozzle.

2. A metallurgical tuyere as claimed in claim 1 wherein said sheath of refractory surrounding said nozzle consists of a layer of low grade refractory cement in contact with said nozzle and a second layer of high grade refractory surrounding said refractory cement.

3. A metallurgical tuyere as claimed in claim 1 wherein the diameter of the discharge passage formed by said sheath of refractory material is substantially the same as the diameter of said nozzle. Y

4. A metallurgical tuyere asclaimed in claim 1 ncluding a highly heat conductive metal stopper member positioned adjacent the inlet end of said central conduit and extending thereinto.

5. A metallurgical tuyere as claimed in claim 1 including an upwardly extending length of pipe connected to the inlet end of said central conduit, the length of said pipe being slightly greater than the anticipated head of molten metal to be treated by said tuyere in a givenheat.

References Cited UNITED STATES PATENTS 2,294,162 8/ 1942 Dobscha 266-42 3,236,629 2/1966 Agarwal et al. 266-41 X 3,264,874 8/1966 Fischer 266-42 X I. SPENCER OVERHOLSER, Primary Examiner. E. MAR, Assistant Examiner. 

